Researchers from the National Heart, Lung, and Blood Institute's (NHLBI) Framingham Heart Study report that mitral-valve prolapse (MVP), a condition in which a valve in the heart is abnormally long and floppy, is substantially less common and less serious than previously believed. In a study appearing in the July 1, 1999 issue of The New England Journal of Medicine, the researchers report that MVP affects about 2 percent of the population rather than the 5 to 35 percent of the population indicated in earlier estimates. And, contradicting earlier studies suggesting that MVP occurs more commonly in women, the researchers found that men and women are equally likely to have the condition. "This is very compelling information," said Dr. Claude Lenfant, Director of the NHLBI, "It may mean people who have been diagnosed with mitral valve prolapse should consult their physician to discuss their health status. It also indicates that further, longer-term studies are called for to resolve this issue definitively and to define the natural history of this condition," he said.
Diagnoses of mitral-valve prolapse increased significantly in the late 1970s and early 1980s with the advent of ultrasound technology which, for the first time, enabled doctors to view the mitral valve noninvasively. According to Dr. Emelia Benjamin, the senior investigator, the earlier studies were conducted using M-mode technology, a form of echocardiography, and often resulted in over diagnosis of MVP. This study was undertaken in part because of the availability of newer, more accurate echocardiographic criteria for mitral-valve prolapse developed by co-author Robert A. Levine, MD. The criteria allowed the researchers to address the validity of the diagnosis of mitral-valve prolapse occurring in an alarming proportion of the population.
Using standard echocardiographic equipment along with the new criteria, which minimizes false positive and false negative diagnoses, the researchers evaluated mitral-valve prolapse status in 3,491 participants in the Framingham Heart Study. Of these, 84 (2.4 percent) had MVP.
"With this study, we may have tempered the notion that mitral-valve prolapse is the most common cardiac valvular abnormality in industrialized countries," said Dr. Lisa Freed, the study's lead author. "In addition, the low frequency of associated complications may allay anxiety for those in whom mitral-valve prolapse is diagnosed in an outpatient setting," she said.
Dr. Benjamin noted the value of conducting this study in a community setting because community studies give a more representative picture of MVP and its clinical features. "Prior studies using echocardiography have involved patients in university hospitals who tend to have more severe abnormalities or symptoms," she said.
In addition to being thought to have a high prevalence rate, MVP has often been portrayed as a disease with frequent and serious complications, including stroke, atrial fibrillation, heart failure. The researchers found that these complications did not occur at higher rates among patients with mitral-valve prolapse compared to those patients without prolapse.
The authors point out that the participants in this study were predominantly white and the results may not apply to other ethnic and racial groups.
Another NHLBI-funded study on MVP appearing in the same issue of The New England Journal of Medicine found that the condition was no more common among young people (45 years old or younger) with stroke or transient ischemic stroke (TIA or mini stroke) than it was among a control group of patients. The issue of a possible connection between MVP and stroke -- especially in young patients -- has been a long-standing controversy. The new study by Dan Gilon, M.D., Robert Levine, M.D. (a co-author of the Framingham study), and colleagues at Massachusetts General Hospital and Harvard Medical School also involved the use of the same new, more accurate echocardiographic criteria. The scientists report that they could not show an association between MVP and acute "ischemic neurologic events" (stroke) in young people.
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